ENZYME ACTION – MEASURING RATE OF REACTION – SUBSTRATE CONCENTRATION

The effects of the following factors on the rate of enzyme controlled reactions – enzyme concentration, substrate concentration, concentration of competitive and of noncompetitive inhibitors, pH and temperature.

Do now: Exam Question

Explain the current model of enzyme action and outline how have models of enzyme action developed.

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how enzymes catalyse reactions by lowering activation energy

- Outline a method for measuring enzyme action in a reaction.

- Analyse results from the substrate rate graph and explain conclusions linking back to the enzyme substrate model.

Activation energy Chemical reactions require a certain

amount of energy to start. This is called the Activation energy.

Enzymes lower the activation energy needed for a reaction to happen. This means that a reaction can happen with less energy input and so reactions will happen quicker.

We call them biological catalysts

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how enzymes catalyse reactions by lowering activation energy

- Outline a method for measuring enzyme action in a reaction.

- Analyse results from the substrate rate graph and explain conclusions linking back to the enzyme substrate model.

How to measure reaction speed?

How could you measure the progress of a reaction? Record the dependent

variable

How could you measure how fast a reaction is happening? Record the dependent

variable every-time you change the independent variable.

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how enzymes catalyse reactions by lowering activation energy

- Outline a method for measuring enzyme action in a reaction.

- Analyse results from the substrate rate graph and explain conclusions linking back to the enzyme substrate model.

How could you measure the rate of reaction for these

enzyme controlled reactions:

1)A reaction that breaks down water into Hydrogen and

oxygen gases2)A reaction that produces

heat the more products made.

3) A reaction that makes products that change colour.

Effect of enzyme concentration on rate of reaction What is the relationship

shown in the graph? Link back to active sites?

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how enzymes catalyse reactions by lowering activation energy

- Outline a method for measuring enzyme action in a reaction.

- Analyse results from the substrate rate graph and explain conclusions linking back to the enzyme substrate model.

In which of these will the rate of reaction be fastest?

Why would not adding anymore substrate make the reaction faster?

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how enzymes catalyse reactions by lowering activation energy

- Outline a method for measuring enzyme action in a reaction.

- Analyse results from the substrate rate graph and explain conclusions linking back to the enzyme substrate model.

Enzyme controlled reactions -substrate concentration

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how enzymes catalyse reactions by lowering activation energy

- Outline a method for measuring enzyme action in a reaction.

- Analyse results from the substrate rate graph and explain conclusions linking back to the enzyme substrate model.

ENZYME ACTION – MEASURING RATE OF REACTION – TEMPERATURE AND PH

The effects of the following factors on the rate of enzyme controlled reactions – enzyme concentration, substrate concentration, concentration of competitive and of noncompetitive inhibitors, pH and temperature.

Do now: Enzyme rates and temperature

Look at this enzyme rate graph. Explain the different phases of each part. Link this back to GCSE knowledge and A-level knowledge

1

2

3

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Describe the term denaturing relating back to active site and enzyme substrate complexes.

- Analyse results from the rate graph and explain conclusions linking back to the protein structure and the enzyme-substrate model.

Effect of temperature on rate of reaction.

Most enzyme controlled reactions require an optimum temperature of 37 degrees celsius.

If lower than this….. And so the rate of these reactions is slower.

If higher than this…. And so the rate of these reactions are slower.

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Describe the term denaturing relating back to active site and enzyme substrate complexes.

- Analyse results from the rate graph and explain conclusions linking back to the protein structure and the enzyme-substrate model.

Denaturing of Enzymes

Why is the shape of the enzyme so important to its function? The substrate has a

complimentary shape that fits exactly into the enzyme so the reaction can happen.

What determines the enzymes/proteins specific shape? The primary, secondary, tertiary

and quaternary structures. What would happen if the

shape of the enzyme changed?

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Describe the term denaturing relating back to active site and enzyme substrate complexes.

- Analyse results from the rate graph and explain conclusions linking back to the protein structure and the enzyme-substrate model.

Denaturing of Enzymes Denaturisation – when

the enzymes active site changes shape and deforms. The substrate is no longer

complimentary The complex cannot form

and the reaction cannot happen

Why does rate of reaction not just drop to zero after 37 degrees?

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Describe the term denaturing relating back to active site and enzyme substrate complexes.

- Analyse results from the rate graph and explain conclusions linking back to the protein structure and the enzyme-substrate model.

pH and rates of reaction

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Describe the relationships between temperature and rate of reaction and pH.

- Describe the term denaturing relating back to active site and enzyme substrate complexes.

- Analyse results from the rate graph and explain conclusions linking back to the protein structure and the enzyme-substrate model.

Acids contain high amounts of H+ ions

Alkalis have high amounts of OH- ions These can interfere with

the structure of the active site and denature the enzymes

ENZYME ACTION - INHIBITORS

The effects of the following factors on the rate of enzyme controlled reactions – enzyme concentration, substrate concentration, concentration of competitive and of noncompetitive inhibitors, pH and temperature.

Do now:

Long answer question:Explain the importance of protein structure in enzyme function and how different factors can affect this.

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how competitive inhibitors decrease enzyme action linking to terms active site and complementary shape.

- Explain how non-competitive inhibition reduces enzyme action by attachment to allosteric site.

- Apply knowledge of inhibition to explain some negative feedback mechanisms.

Mini – Practical:1) Add the catalase to the hydrogen

peroxide, measure how much oxygen is produced in a minute.

2) To the catalase, add 20mls of copper sulphate solution, leave for 3 minutes. Now add the hydrogen peroxide and measure in a minute.

Inhibitors

Chemicals that bind to an enzyme and reduce its activity.

Competitive Inhibitors Bind to the active site just like

a substrate would

Non competitive inhibitors. Bind to the allosteric site

permanantly and denature the active site.

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how competitive inhibitors decrease enzyme action linking to terms active site and complementary shape.

- Explain how non-competitive inhibition reduces enzyme action by attachment to allosteric site.

- Apply knowledge of inhibition to explain some negative feedback mechanisms.

Competitive Inhibitors Have a complimentary shape just like a

substrate. ‘compete’ with the substrate to bind with

the enzyme. When substrate concentration increases,

the inhibitors are less effective.

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how competitive inhibitors decrease enzyme action linking to terms active site and complementary shape.

- Explain how non-competitive inhibition reduces enzyme action by attachment to allosteric site.

- Apply knowledge of inhibition to explain some negative feedback mechanisms.

Competitive Inhibitors

Vmax value is the same for normal enzyme and an enzyme inhibited competitively.

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how competitive inhibitors decrease enzyme action linking to terms active site and complementary shape.

- Explain how non-competitive inhibition reduces enzyme action by attachment to allosteric site.

- Apply knowledge of inhibition to explain some negative feedback mechanisms.

Non- Competitive Inhibitors

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how competitive inhibitors decrease enzyme action linking to terms active site and complementary shape.

- Explain how non-competitive inhibition reduces enzyme action by attachment to allosteric site.

- Apply knowledge of inhibition to explain some negative feedback mechanisms.

The inhibitors bind at the allosteric site, not the active site!

They cause the shape of the active site to change (denature)

Substrates cant bind anymore, no matter how much substrate you add.

Non- Competitive Inhibitors

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how competitive inhibitors decrease enzyme action linking to terms active site and complementary shape.

- Explain how non-competitive inhibition reduces enzyme action by attachment to allosteric site.

- Apply knowledge of inhibition to explain some negative feedback mechanisms.

The vmax is half of what a normal enzyme reaction would be.

Negative feedback of Enzyme Inhibition

What does negative feedback mean? The products of an enzyme reaction feedback

and act as inhibitors for the enzyme to stop too much reaction happening

In what process do you think this is important?

Outcomes:- Recall enzyme

structure and the mechanism of the enzyme substrate complex.

- Explain how competitive inhibitors decrease enzyme action linking to terms active site and complementary shape.

- Explain how non-competitive inhibition reduces enzyme action by attachment to allosteric site.

- Apply knowledge of inhibition to explain some negative feedback mechanisms.